Special Procedures Core: A Special Procedures Core will be set up to provide specialized services required by various investigators of the Program Project Grant. The Special Procedures Core will a) continue the services provided by the current PPG Tissue Culture Core and b) evaluate new patients for possible defects in their GH peptide, IGF-I peptide, GH binding protein, and/or tissue responsiveness to IGF-I utilizing procedures established in Project 2 of the current PPG. The culture facility will continue to establish fibroblast strains (est. 12/y) from selected short stature patients with possible defects in their GH/IGF-I tissue responsiveness. Various cell strains will be cultured for the experiments proposed in Projects 2, 4, and 5. Project 2: Methods were developed in the PPG for evaluating the receptor reactivity of the GH and of the IGF-I present in patients' sera, the level of circulating GH-BP, and the IGF-I responsiveness of patients' fibroblasts. These methods provide more complete characterization of the GH/IGF-I status of short stature patients and identify those patients who should receive more in depth investigation by the appropriate PPG project. It is proposed that the Special Procedures Core assume responsibility for these evaluations of new short stature patients. The receptor reactivity of serum GH and IGF-I is determined from the ratio of their reactivity in a receptor assay as compared to reactivity in an IRMA assay. The level of serum GH binding protein is measured by gel filtration separation of bound 125I hGH. The IGF-i responsiveness of patient fibroblast is evaluated with IGF-I dose assays for stimulation of fibroblast uptake of AIB. It is estimated that 20-30 short stature patients will be evaluated by the core annually with selected tests being performed based upon the patient's serum GH and IGF-I levels. These evaluations will also be performed as needed for subjects under the study by Project 8 which is investigating regulation of fetal growth.